The present invention relates to three position retaining valves and more specifically to improvement thereon.
The retaining valve is a valve connected to the exhaust output of the pipe bracket of a pneumatic rail brake. The retaining valve controls brake cylinder exhaust rate or maintains, for example, a 20 PSIG brake cylinder air pressure as controlled by the position of the manually operated valve handle. Although four positions have been used, the present American Association of Railroads ("AAR") standards are three positions, namely, direct exhaust, slow direct and high pressure retain. A typical example is illustrated in FIG. 1 and is available from New York Air Brake, having part number NY-3. The valve includes a body 10 with a mounting bracket 12. A first bore 14 is connected to an inlet 16 which receives the pressure to be exhausted or retained and a second bore 18 is connected to outlet 20 which is covered by cover 22. A ball valve element 24 is in the first bore 14 and has a handle 26 connected thereto by nut 28. Detent 30 is received in the recess 32 of the handle 26. A spring 34 is connected between snap ring 36 and the ball valve 24. A slide 38 cooperates with valve seat 40 and is biased by spring 42 to its open position. Appropriate passages in the ball valve 24 connects the first bore 14 to the second bore 18. Slide 38 is responsive to the pressure in the first bore and disconnects the communication between the first bore 14 via ball valve 24 and the outlet 20 when the pressure in bore 14 is above 20 PSIG. The body 10, the valve element 24, the handle 26 and the slide 38 are all made of metal.
The valve element may also be cylindrical instead of a ball valve element and include the slide in a bore within the cylinder as shown in FIG. 13 of U.S. Pat. No. 3,532,117. To reduce the cost from the cast iron bodies and other metal parts, it has been suggested to make the body, handle and valve element out of plastic in U.S. Pat. No. 5,228,648.
The present invention is a retaining valve having various improvements. One of the improvements is the structure of the slide and its seal. The valve element is received in a first bore of the body and includes a second bore having the slide therein. The valve element is rotatable by handle between first, second and third angular positions connecting the inlet of the housing to the outlet through first, second and third passages in the valve elements respectively for each of the angular positions. The slide extends from a point between the inlet and the connection of the first, second and third passages to the second bore to a point past the connection of the first, second and third passages to the second bore with respect to the inlet. A seal is at a position on the slide which is past the connection of the first and second passages to the second bore with respect to the inlet for all positions of the slide and which is past the connection of the third passage to the second bore with respect to the inlet only when the inlet pressure is above a minimal level. Preferably, the body, valve element and slide are made of plastic and the handle is a unitary one piece with the valve element.
Another improvement is the retention of the valve element in the body with respect to axial movement. The retainer includes a first ring concentric to the valve element and having a radial flange engaging the body at a first surface of the flange. A snap ring is mounted on the valve element adjacent to a second facing the flange. The first ring is fixed to rotate with the valve element. A spring is provided between a first end of the slide and an end wall of the second bore and a stop is provided in the second bore adjacent to the second end of the slide. The stop includes a pin extending from the valve element across the second bore. The first ring is concentric to and retains the pin on the valve element.
Another improvement to the retaining valve is wherein the handle includes a race having a first and second ends and the body includes a stop riding in the race and engaging the ends of the race at the first and second angular positions of the valve element respectively. A detent is also provided between the handle and the body locking the valve element in the first, second and third angular positions.
These improved structures allow an improved method of assembly. A method of assembly includes inserting the valve with the handle thereon in a first end of the first bore of the housing. The slide is inserted in the second end of the second bore in the valve element and a stop for the slide is inserted adjacent the second end of the second bore. The retainer is applied adjacent the second end of the valve element and a second end of the first bore to secure the valve element to the body with respect to the axial movement. The spring is inserted in the second end of the second bore before the insertion of the slide. The stop is a pin which is inserted in the pair of opposing holes in the valve element and the retainer is applied concentric to the pin to retain it in the valve element. The retainer includes the first ring mounted concentric to the valve element with its radial flange engaging the body at a first surface of the flange. The snap ring is then mounted on the valve element adjacent the second face of the flange.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.